Much of the 4chan leaker's information about Origins was bang on the nose. They even set the next game (Odyssey) in Ancient Greece directly after having one in Ancient Egypt. If they're doing an "ancient trilogy" it would make sense to do the Roman Empire because they can recycle assets from Origins and Odyssey.

I'd heard last year from three different people familiar with goings-on at Ubisoft that the next big Assassin's Creed would be set in ancient Egypt. Since this morning, two other independent sources have contacted me to corroborate that. I heard about the code name Empire from two of those sources. Three of them told me the game would indeed launch in 2017. Months ago, one source told me the game would also take place in ancient Rome, although that may have changed; the 4chan poster says some sections had been removed from the game. ("There are talks about making a trilogy of this same character, so they might explore Greece/Rome next," the poster wrote.)

Ancient Rome would be an entirely different beast from Renaissance era Italy from the Ezio trilogy, so that'd be great to see.

Hopefully for a truly next gen (PS5) AC we can finally get feudal Japan.

Origins was already somewhat set in the roman empire (well roman republic to be precise). If they do set it in the roman empire and set it in rome itself, then perhaps set it in the 4th century during the early Christian era.